High precision micro-optical elements on fiber facets via focused-ion beam machining

Abstract:Fiber-integrated micro-optical elements promise a scalable approach to photon collection and beam shaping for quantum information processing. Here, we demonstrate single-step micro-machining of micro-spherical, micro-spiral, and micro-axicon structures directly onto the core of single-mode optical fibers using focused-ion beam (FIB) machining with nanometer-scale precision. Atomic force microscopy reveals that micro-concave and micro-convex spherical surfaces achieve shape accuracies of $\lambda/50$ and $\lambda/33$ (at $\lambda = 633$~nm), respectively. Via optical characterization using a He-Ne laser (633~nm), we verify for the micro-spiral and -axicon structures the expected far-field donut beam patterns. Via Mach-Zehnder interferometry, we verify the azimuthal and radial phase structure of the light emitted from the spiral and axicon fibers, respectively. Surface metrology further shows that FIB processing introduces only a small increase in nanoscale roughness while preserving sub-nanometer RMS surface quality. The monolithically integrated fiber micro-optic elements demonstrated here enable broad use in quantum technology, for example, fiber micro-cavities for cavity quantum electrodynamics, beam shaping for neutral atom trapping, and the generation of structured light for free-space quantum network links.

Optics (physics.optics); Applied Physics (physics.app-ph); Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)

arXiv:2604.18426 [physics.optics]

(or arXiv:2604.18426v2 [physics.optics] for this version)

https://doi.org/10.48550/arXiv.2604.18426 Focus to learn more arXiv-issued DOI via DataCite

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